# Neural underpinnings of the interplay between actual touch and action imagination in social contexts

## TL;DR

This study explores how touch and imagined actions interact in the brain, particularly in social situations, revealing how the motor system responds differently to various types of touch.

## Contribution

The study introduces a novel approach to understanding how touch and action imagination interact in social contexts using transcranial magnetic stimulation.

## Key findings

- Touch experience increases M1 excitability during imagined force production.
- Biological touch sources (self and others) significantly elevate motor activity compared to non-living surfaces.
- Touch avoidance correlates with motor system facilitation during interpersonal touch.

## Abstract

While there is established evidence supporting the involvement of the sense of touch in various actions, the neural underpinnings of touch and action interplay in a social context remain poorly understood. To prospectively investigate this phenomenon and offer further insights, we employed a combination of motor and sensory components by asking participants to imagine exerting force with the index finger while experiencing their own touch, the touch of one another individual, the touch of a surface, and no touch. Based on the assumption that the patterns of activation in the motor system are similar when action is imagined or actually performed, we proceeded to apply a single-pulse transcranial magnetic stimulation over the primary motor cortex (M1) while participants engaged in the act of imagination. Touch experience was associated with higher M1 excitability in the presence and in the absence of force production imagination, but only during force production imagination M1 excitability differed among the types of touch: both biological sources, the self-touch and the touch of one other individual, elicited a significant increase in motor system activity when compared to touching a non-living surface or in the absence of touch. A strong correlation between individual touch avoidance questionnaire values and facilitation in the motor system was present while touching another person, indicating a social aspect for touch in action. The present study unveils the motor system correlates when the sensory/motor components of touch are considered in social contexts.